Coated lamp



M. PlPKlN COATED LAMP Feb. 19, 1957 Filed Oct. 1, 1953 lnvent on: ManvinPipKin, y W K His Attorney United States Patent Ofi 2,78 1,654 PatentedFeb. 19, 1957 COATED LAMP Marvin Pipkin, Granger Township, MedinaCounty, Ohio, assignor to General Electric Company, a corporation of NewYork Application October 1, 1953, Serial No. 383,529

9 Claims. (Cl. 67-31) My invention relates to electric lamps in generaland particularly to lamps of the incandescent and photoflash type andmore particularly to indicating and light-diifusing protective lacquercoatings for said lamps.

This application is a continuation-in-part of my application Serial No.352,259, filed April 30, 1953, now abandoned, and assigned to theassignee of this application.

In flash lamps for example of the type comprising a bulb or envelope ofglass or similar material and containign a charge of readily combustiblelight-giving material which, on ignition, burns with great rapidity toproduce a momentary flash of actinic light, the bulb is customarilyprovided with a protective coating of a suitable material such as alacquer for instance. A protective coating or lacquer is applied to theinterior bulb wall as well as the outside bulb surface in order tostrengthen the bulb and prevent the cracking thereof, upon chargeflashing, by hot burning particles of the combustible material. Sincethe lacquer coatings preferably used on the interior of the bulbs are ofa clear or colorless character, it is difficult to detect which bulbshave and which have not been provided with an interior coating. Thisdifiiculty is particularly troublesome in the mass productionmanufacture of such type lamps where, because of the large numbers ofbulbs handled, uncoated bulbs are apt to become intermingled with coatedbulbs and processed and made into finished lamps in the usual way. Suchuncoated lamps would then be hazardous because of the possibility of thebulb cracking and exploding on charge flash with resultant danger ofinjury, either to the user or the subject being photographed, fromflying glass fragments.

The protective lacquer coatings applied to the outer bulb surface havealso usually been of a clear or colorless character thus requiring ahigh degree of clarity in the finished lamp to be acceptable to theultimate consumer. These previously used outside lacquer coatings havealso failed to provide any diffusion of the actinic light generated uponflashing of a lamp.

It is one object of my invention, therefore to provide a flash lamp ofthe above-described character having a lighttransmitting bulb providedwith an interior protective coating the presence of which is readilyascertainable and which is substantially clear and colorless in thefinished lamp.

Another object of my invention is to provide a bulb for a flash lamp orother lamp device having a protective coating on its inner surface whichis substantially visible under normal lighting conditions duringmanufacture, but which can be rendered invisible by curing with heatprior to final assembly of the lamp components.

Still another object of my invention is to provide a lacquer coating onthe outer surface of bulbs used in electric lamps capable of protectingthe bulb surface and also acting as a light-diffusing film.

A feature of the invention in one of its aspects is the application ofan interior lacquer coating to a flash lamp bulb, for example which,when dried in air, assumes a frosted or white color, thus permittingvisual inspection to determine that the interior coating has beenapplied, and also permits a rapid, visual quality check on the thicknessand distribution of the coating. When the bulb is sufficiently heated toobtain a proper cure prior to final assembly of the lamp components, theinside lacquer, made according to one aspect of my invention, becomesclear or transparent similar to other lacquers used for such purpose.

Another feature of my invention is the application of an externallacquer coating to electric lamp bulbs, incandescent as well asphotoflash, which assumes a frosted, white appearance upon air dryingand thus diffuses the light generated by the lamps with no material lossin light output. This outside coating also strengthens and protects thebulb, resists heat and indicates uniformity of thickness of the appliedfilm. The usual clear, protective lacquers applied to theouter surfaceof flash lamps, for example, have been difficult to apply uniformly and,after application, the lack of uniformity has been virtually impossibleto detect. This lack of uniformity frequently results in numerous thinspots in the lacquer coating thereby destroying its utility as a bulbstrengthener or in containing the glass fragments should the bulbshatter. The frosted exterior lacquer of my invention gives a positivevisual indication when uniformity of thickness is lacking in that anythin spots in the coating show up as clear, colorless areas which, incontrast to the frosted surrounding film, are readily detectable.

The frosted or white character of the external lacquer can be regulatedby variations in the lacquer composition to obtain a film ranging from avery light frosting to a pure white.

Further objects and advantages of my invention will' appear from thefollowing description of a species thereof and from the accompanyingdrawing in which:

Fig. l is an elevation of a flash lamp illustrating one feature of myinvention,

Fig. 2 is a-fragmentary sectional view of the bulb thereof, and

Fig. 3 is an elevation, partly in section, of an incandescent lamphaving a bulb coated in accordance with one aspect of my invention.

Referring to the drawing, the invention is there shown as applied to aflash lamp (Fig. l) of the type comprising a sealed light-transmittingbulb or envelope 1 of glass or other suitable material and provided atits neck end 2 with a re-entrant stem 3 which extends into the bulb andterminates at its inner end in a press or seal :portion 4 through whichare sealed a pair of lead-in wires 5 and 6 connected at their outer endsto the center contact 7 and shell 8, respectively, of a base 9 cementedor otherwise secured to the neck end of the bulb. The said lead-in Wires5, 6 extend into the bulb in more or less side-by-side relation and areprovided at their inner ends with an ignition means It which maycomprise a filament 11 connected across the lead-in wires and consistingof a short length of tungsten wire, for instance. The inner ends or tipsof the lead-in wires 5, 6 are pro vided with small beads or coatings 12of a suitable primer or fulminating material such as, for example, amixture of zirconium, magnesium and potassium perchlorate powders bondedtogether by a suitable binder such as nitrocellulose. The primer beads12 are located on the lead-in wires 5, 6 at the region of the connectionof the latter to the filament 11 so as to embed at least the endportions of the filament 11 and thus become ignited thereby upon passageof an electric current through the filament.

Disposed within the bulb 1 and around the ignition means 10, so as to bewithin effective ignition range thereof, is a charge of readilycombustible light-giving material 13, such as leaf foil, wire, shreddedfoil, or ribbon which, on ignition by the igniter means 10, burns withgreat rapidity to produce a momentary flash of actinic light. In theparticular lamp illustrated, the light-giving material 13 comprises aloose filling of filamentary material (such as shredded foil forinstance) of a readily combustible composition, such as aluminum,magnesium or alloys thereof. The bulb 1 further contains a gas filling,such as oxygen for instance, at a suitable pressure for supportingcombustion of the charge 13 of light-giving material.

To strengthen the bulb and minimize cracking thereof upon chargeflashing, and also to prevent scattering of glass fragments in case thebulb actually should explode during flashing, the bulb 1 is coatedinteriorly, and exteriorly as well, with protective coating 14 and 15,respectively (Fig. 2), of suitable materials, such as a lacquer forinstance. In the past these protective coatings 14 and 15 have been of aclear or transparent character; however, I prefer that either or both ofthese coatings be of a frosted, light-diffusing character. This frostedeffect may be of a temporary nature, as illustrated below with respectto interior coatings, or permanent as mentioned later in regard to bothinterior and exterior lacquers.

Another feature of my invention is illustrated in Fig. 3 which is aconventional incandescent lamp having a sealed glass bulb 16 containinga tungsten filament 17, said bulb 16 being either gas-filled orevacuated. A translucent coating 18 of my invention is shown as appliedto a surface of said bulb 16 to diffuse the light and strengthen theglass.

In the production manufacture of flash lamps of the type describedabove, the bulb 1 is first provided with the inside coating 14 byspraying or other suitable means after which the charge 13 ofcombustible material is introduced into the bulb through the open neckend thereof, the stem 3 then sealed into the bulb which is filled withoxygen, and the base 9 attached thereto and the lamp then coatedexteriorly with lacquer. Because of the transparent, and thereforeundetectable character of the inside coatings previously used, it isdifficult to determine, during subsequent manufacturing operations,whether ornot such an inside coating is actually present in the bulb. Asa result, uncoated bulbs are apt to become fabricated into finishedlamps which, if subsequently detected and discarded, represent amanufacturing loss on the one hand, but if not detected and discardedare potentially dangerous to the ultimate consumer because of thepossibility of the uncoated bulb cracking and exploding on flashing ofthe lamp.

In order to permit ready detection of the presence of the insideprotective coating 14 in the bulb prior to introduction of thecombustible material 13 and sealing of the stem 3 into the bulb, thesaid coating 14 is formed in accordance with one aspect of the inventionof a material which, when dried in air, assumes a non-transparentcharacter, for instance a frosted or white color, and yet when properlycured with heat prior to assembly of the lamp assumes a clear ortransparent character. Thus, when bulbs are cured just prior to finallamp assembly, a rapid visual inspection will insure that onlyinteriorly frosted bulbs are cured and assembled, eliminating thepossibility of a lamp being assembled without an interior protectivecoating. It will be noted that the curing step may be omitted, therebyleaving the interior film in a frosted condition without eliminating thebenefits of fast and accurate visual inspection. The advantage to begained by this latter practice is that the frosted film acts as anexcellent diffuser of the light generated by the lamp and this lightdiffusion is accomplished with little or no loss of light output.

After the bulb is inspected to determine the presence and uniformity ofthe interior coating, it may be cured,

combustible material introduced into the bulb, the stem sealed in andthe base attached. At this point the bulb is coated exteriorly with asuitable outside lacquer 15. In the past, these outside lacquers havealso been of a clear, colorless character. Thus, when both inside andoutside protective lacquers are colorless, it is essential that the lampbe crystal clear to be acceptable to the consumer, thereby necessitatingthe rejection of all lamps bearing slight blemishes although theseblemishes would have no effect on lamp performance. This difficultywould be completely eliminated by the application of the frosted lacquerof my invention to exterior bulb surfaces accompanied by the aforesaidadditional advantages, such as excellent light diffusion with no loss inlight output and increased strength and heat resistance. The clearlacquers previously employed as exterior protective coatings had afurther disadvantage in that extremely thin coating frequently occurs insmallareas on the bulb surface, which areas are virtually undetectableand considerably reduce the effective protection afforded by thecoating. The frosted lacquer of my invention is self-indicating due toits property of becoming colorless when applied in extremely thin films.Thus, any thin areas that occur on application of the lacquer arevisually detectable as clear spots in contrast to the surroundingfrosted film. Rapid visual inspection can easily determine thesufficiency and uniformity of the frosted exterior protective coating.

I have found that lacquer compositions heretofore employed may bemodified in a manner to achieve the desired results. For example, awell-known interior lacquer comprising a mixture of polymerized vinylester and cellulose nitrate may be modified by the addition thereto ofhydrolyzable silicic acid esters as clouding agents. I have found thatthe tetraethyl ester of ortho-silicic acid (tetra ethyl ortho-silicate,(C2H5)4Si04) hereinafter referred to as ethyl silicate, is the preferredester due to the ease and facility with which it accomplishes theobjects of the invention, its commercial availability and relativeeconomy. Similarly, all well-known exterior lacquers, such as celluloseacetate for example, may be modified in the same manner.

Good results may be attained when the interior surface of a bulb iscoated with a lacquer comprising essentially about 300 to 400 parts byweight polymerized vinyl acetate (Vinylite) resin solution, about 5 tolOO parts by weight acetone, about 20 to 70 parts by weight alcohol,about 93 to 146 parts by weight nitrocellulose solution. and about 50 to150 parts by weight ethyl silicate. Excellent protective and diffusingcoatings result when exterior bulb surfaces are covered with a lacquercomprising acetone, alcohol, cellulose acetate and ethyl silicate.Specific examples of representative interior as Well as exterior lacquercompositions according to my invention are as follows:

The nitrocellulose solution used in the specific example consists ofl6l7.5% of 5 to 6 second grade dry nitrocellulose dissolved in equalparts of ethyl and isopropyl acetate. This solution has a viscosity of50 to 65 seconds at 25 C. in a #20 Parlin cup.

The acetone is added as a thinner and the amount used may vary over afairly wide range according to the desired lacquer viscosity which alsoprovides a means of controlling the thickness of the interior coatingapplied. The alcohol of the example is l90-proof denatured ethanol. Theamount of alcohoi used should not exceed an upper limit of around 10% byweight of the total mixture, since too great an excess Will cause thesolids to come out of suspension. The amount of nitrocellulose usedshould not exceed about 20% by weight of the total mixture, becausegreater amounts tend to cause a blackening or charring of the insidelacquer coating when the bulb is heated to seal in the stem portion.However, a sufficient amount should be used to harden the Vinylite,otherwise the coating will not have the requisite strength.

It will be noted that the composition is not limited with respect tovolatile solvents and diluents since other materials of the typeillustrated in the example including esters and ketones, such as methylacetate, ethyl acetate, methylethyl ketone, and diluents such as butylalcohol, toluol, etc. may be used provided sulficient active solvent ispresent to afford complete solution of the nitrocellulose. Nor is thecomposition limited with respect to the principal lacquer ingredientssince other lacquers, such as acrylic acid esters, cellulose esters andmixtures of vinyl resins and cellulose ester lacquers, may also bemodified with ethyl silicate.

Example B.Exterir lacquer The solvents are mixed in the followingproportions:

Cellulose acetate is added to the above mixture as follows:

Percent Pounds by Weight (Total) Cellulose Acetate 11 15 After thecellulose acetate has been dissolved in the solvents, ethyl silicate isadded in amounts of about 200 cc. per gallon of lacquer which in theabove specific example would amount to about 1.84 liters.

The acetone of the above example is the principal solvent for celluloseacetate, being very active and possessing a high evaporation rate. Asuitable solvent for cellulose acetate possessing similarcharacteristics, such as ethylene dichloride or tri-cresol phosphate forexample, may be substituted. Denatured alcohol (190-pr0of ethanol) isadded as a latent solvent and it will be understood that other suitablelatent solvents, such as isopropyl alcohol for example, may besubstituted. The ethyl silicate may range from 15 to 400 cc. per gallonof lacquer depending on the degree of opacity desired. The density ofthe frosted effect may thus be varied from very light to a dense, almostpure white.

In previous lamp lacquers of the clear or colorless character, adiscoloration frequently occurred which was commonly known to thoseskilled in the art as blushing." This was caused, at least in part, bytoo rapid evaporation of the solvents and as a remedy an additionalsolvent for the principal lacquer ingredient, having a low evaporationrate but capable of complete evaporation, was added. In Example B,di-acetone alcohol as a solvent for cellulose acetate Was found topossess the desired properties to prevent blushing. Ethyl lactate isanother example of a solvent suitable for this purpose. However, sincethe lacquer of my invention as illustrated in Example 13 possesses afrosted, white character, blushing" may not prove detrimental, thuseliminating the necessity for the addition of this 'lattervtype solvent.

It will be further understood that this feature bf m invention is notlimited to lacquers of the type illustrated. I have discovered thatpractically all lacquers suitable for coating glass surfaces, such asacrylic acid esters (methacrylatesand Acryloids for example), celluloseesters and mixtures of vinyl resins and cellulose esters, may bemodified with ethyl silicate to produce the desired diffusing effect. Ihave also found that certain other compounds may be added to thelacquers of my invention to enhance certain desirable properties. Forexample, up to 10% by weight sucrose oota acetate may be added toimprove the abrasion resistance of the lacquer film thus rendering itless susceptible to weakening scratches and checks. This addition alsoimproves the moisture resistance and prevents the formation of smallbubbles in the film. .Although the heat resistance of lacquer films isgreatly improved by the addition of ethyl silicate, in lamps whereconsiderable heat is rapidly generated such as photofiash lamps, somecharring or bubbling of the lacquer film does occur. This effect may bereduced by the addition of tri-phenyl phosphate in amounts of about 10%by weight. The moisture resistance and toughness of' the film is alsoimproved. The addition of small amounts of polyethylene terephthalate isalso beneficial in that the strength of the lacquer is greatly increasedthus permitting the use of thinner films while affording the same orgreater degree of protection and effecting an economy in lacquermaterials. This material also improves the dimensional stability of thelacquer, thereby reducing the tendency of the film to expand or contractand separate from the glass with variations in temperature.

In the manufacture of flash lamps in accordance with one aspect of theinvention, the interior of the bulb 1 is coated with lacquer 14, forexample that illustrated in Example A, by spraying or other suitablemeans, the lacquer then being air dried until it assumes a frosted orWhite color. The linteriorly coated bulbs are then transferred to theassembly point where they are cured with heat prior to being filled withthe charge of combustible material. Inspection prior to the curingoperation and discarding all bulbs not having a frosted or whiteinterior color, or which are only partially white colored, will preventunlacquered and incompletely lacquered bulbs from being fabricated intofinished lamps. After the curing operation the bulbs may be againinspected to ascertain that the interior coating has been properlycured. That has been accomplished when the lacquer has assumed acompletely clear or transparent character. Rejection of cloudy bulbsprior to assembly of the lamp components, coupled with the previouslymentioned discarding of unlacquered and incompletely coated bulbs priorto curing, thus prevents the fabrication of these bulbs into lamps whichwould be of defective and potentially dangerous construction. Themodified lacquer allows the inspection of the bulbs for presence ofinside coating prior to scaling of the stem and attachment of the basethereto, which :is preferable because of the saving in time as well asstems and bases Which otherwise would be discarded along with the bulbif the lamp were finished before inspection, thus reducing manufacturingcosts. After inspection, curing and completion of the lamp as described,a suitable lacquer is customarily applied to the exterior surface tofurther strengthen and protect the lamp.

in the curing operation mentioned above, the interiorly coated bulb isheated at about 60-70 C. for a period of about 3-8 minutes, preferably 5minutes. A proper cure has been achieved when the frosted interiorcoating has assumed a completely clear or transparent appearance. Thecuring step also serves to remove excess solvent in the lacquer.

If a diffusing coating is desired, the interior lacquer of Example A maybe left in the frosted condition by elimination of the curing step. Thisalso eliminatesv the '7 necessity for the second inspection to determinecomplete curing while retaining the benefits and ease of the firstinspection. The lacquer of Example B may also be applied to the interiorof the bulb if a permanently frosted coating is desired with the samebeneficial results as the lacquer of Example A.

While the reactions are complex and have not been definitelyascertained, it is believed that the desired frosted appearance isachieved on air-drying of the lacquer of the type illustrated in ExampleA by the evaporation of the solvents (acetone and alcohol) leavingVinylite, nitrocellulose and ethyl silicate as a three-component,immiscible system in which the said immiscibility of the componentsrather than any particular component produces the frosted appearance.Upon curing the air-dried film as previously mentioned, the ethylsilicate, which is the most volatile component of the immiscible system,evaporates leaving what appears to be a colorless solution of Vinyliteand nitrocellulose which are apparently miscible, rendering the finalheat-cured lacquer film clear and colorless.

In lacquer compositions of the general type illustrated in Example B,customarily used to coat the exterior surface of glass bulbs and thelike, the reactions are somewhat different. The permanently frostedappearance is produced on air-drying of the lacquer, possibly bybydrolysis of the ethyl silicate. That is, the ethyl silicate in thelacquer decomposes in moisture present in the alcohol or in the air,forming a hydrate of silica, possibly silicic acid (an insoluble whitepigment) or some compound of silica and water, which produces thepermanently frosted or white color in the lacquer. Thus, nor malheatcuring at temperatures of about 60 C. does not affect the frostedcondition. Even at considerably elevated temperatures of about 300 C.only a small amount of water is driven off and, although there may besome change in the crystal structure of the silica compound, the lacquerretains its frosted appearance.

While I have generally shown and described the invention as applied toflash lamps and particularly those of the type having a loose filling ofcombustible material, such as wire, ribbon, shredded foil or leaf foil,it should be understood that the invention is applicable to any type ofphotofiash lamp containing combustible material such as, for example,those of the so-called primer type as dis closed in U. S. Patent No.2,291,983, Pipkin, wherein the combustible material is in the form ofsmall beads or coatings of a fulminating paste provided on the innerleads of the lamp and embedding at least the end portions of theignition filament.

However, or greater significance and of primary importance is theapplication of my invention to all types of incandescent lamps. Forinstance, lacquer coatings of the type shown in Example B may be appliedeither to the inner or outer surface of ordinary incandescent lamp bulbsto provide protection for the bulb and efficiently diffuse the light,thereby reducing bright spots or glare from the incandescent filamentwith-out noticeable loss in light output. Thus, a controlled degree ofopacity may be easily obtained in the lamp by applying the lacquer of myinvention using any well-known means of lacquering glass such asspraying, dipping, etc., without acid etching or depositing silicapowder inside the bulb by combustion of a silica compound. Also, thefrosted coating, whether on the inner or outer surface of the bulb, maybe readily inspected for uniformity. any thin spots in the coatingshowing up as clear areas on the bulb surface in contrast to thesurrounding frosted coating.

In miniature incandescent lamps, such as flash light lamps for instance,the protective, light-diffusing coating of my invention is particularlyuseful since the extremely small size of the bulb renders acid etchingor the deposition of powdered silica extremely difficult.

I have found in addition that color pigments may be added to thelacquers of my invention, making it possible to produce any desiredshade or color in the frosted, light-diffusing film which is uniform,vivid and pleasing to the eye. This aspect of my invention hasparticular application to Christmas tree lamps in that, in addition tostrengthening the bulb and producing any desired color, it isconsiderably more economical than the enameling method previouslyemployed. In both the miniature and Christmas tree incandescent lamp theadvantages of ease and rapidity of visual inspection are present to thesame degree as in other types.

Although preferred embodiments of my invention have i been disclosed, itis recognized that variations and changes may be made therein within thespirit and scope of the invention as defined by the appended claims.

It is understood further that the ingredients, their proportions asgiven above and also the times and temperatures can be varied,independently and in relation to each other, within fairly wide limitsto obtain the desired results. Further, it will be particularlyrecognized that my invention is not limited with respect to principallacquer ingredients, good results being obtained with any type lacquersuitable for application to glass surfaces such as for example,methacrylates, Acryloids, cellulose esters, mixtures of vinyl resins andcellulose esters, and other thermo-setting or thermoplastic lacquers.

What I claim as new and desired to secure by Letters Patent of theUnited States is:

1. An electric lamp comprising a glass bulb containing a light sourceand having thereon a coating of an organic lacquer comprisingessentially the dried product of a material selected from the groupconsisting of the acrylic acid esters, cellulose esters and mixtures ofvinyl resins and cellulose esters, and about 15 to about 400 cubiccentimeters of the tetraethyl ester of ortho-silicic acid per gallon ofsaid lacquer.

2. An electric lamp comprising a glass bulb containing a light sourceand having on said bulb a coating of an organic plastic lacquer composedessentially of the dried product of a material selected from the groupconsisting of the acrylic acid esters, cellulose esters and mixtures ofvinyl resins and cellulose esters, and about 15 to about 400 cubiccentimeters of an ester of silicic acid per gallon of said lacquer.

3. An electric lamp comprising a glass bulb containing a light source, asurface of said bulb having thereon a translucent coating of an organiclacquer material comprising the dried product of a cellulose ester,solvents therefor and about 15 to about 400 cubic centimeters of anester of silicic acid per gallon of said lacquer material.

4. An electric lamp comprising a glass bulb containing a light source, asurface of said bulb having thereon a translucent coating of an organiclacquer material consisting essentially of the dried product ofcellulose acetate, acetone, alcohol and about 15 to about 400 cubiccentimeters of tetraethyl ester of orthosilicic acid per gallon of saidlacquer material.

5. An electric lamp comprising a glass bulb containing a light source,the exterior surface of said bulb bearing a translucent coating oforganic lacquer consisting of the dried product ofa mixture of aboutparts by weight acetone, about 10 parts by weight alcohol and about 10parts by weight di-acetone alcohol in which is dissolved about 15 partsby weight dry cellulose acetate, and about 15 to about 400 cubiccentimeters of tetraethyl orthosilicate per gallon of said lacquer.

6. A flash lamp comprising a substantially clear glass envelopecontaining a quantity of readily combustible material adapted togenerate on combustion a flash of actinic light, said envelope havingits interior surface provided with a coating consisting of theheat-cured product of an air-dried film of a lacquer material consistingessentially of a polymerized vinyl ester, about 15 to about 400 cubiccentimeters of hydrolyzable silicic acid ester per gallon of saidlacquer material, cellulose nitrate solution, and thinners therefor.

7. A flash lamp comprising a substantially clear glass envelopecontaining a quantity of readily combustible material andcombustion-supporting means adapted to generate on combustion a flash ofactinic light, said envelope having its interior surface provided with acoating consisting of the heat-cured product of an air-dried film of alacquer material consisting essentially of polymerized vinyl acetateresin solution, about 15 to about 400 cubic centimeters of tetraethylester of ortho-silicic acid per gallon of said lacquer material,cellulose nitrate solution, alcohol and a thinner therefor.

8. A flash lamp comprising a substantially clear glass envelopecontaining a quantity of readily combustible material andcombustion-supporting means adapted to generate on combustion a flash ofactinic light, said envelope having its interior surface provided with acoating consisting of the heat-cured product of an air-dried film of alacquer material consisting essentially of about 300 to 400 parts byweight polymerized vinyl acetate resin solution,

about 93 to 146 parts by weight, not ex- 2 10 ceeding of total weight,cellulose nitrate solution, about to 150 parts by weight ethyl silicate,about 20 to parts by weight, not more than 10% of total weight, alcohol,and about 5 to parts by weight acetone.

9. A bulb for electric lamps and similar articles made of clear glass,and a frosted white protective lacquer coating on the inner surface ofsaid bulb, said coating having the property of becoming clear andcolorless when subjected to heat of about 6070 C. for about 5 minutes,said coating comprising essentially the dried product of a polymerizedvinyl ester, about 15 to about 400 cubic centimeters of ethyl silicateper gallon of said lacquer coating, cellulose nitrate solution, alcoholand a thinner therefor.

Lurlander July 7, 1936 Pipkin Oct. 16, 1951

2. AN ELECTRIC LAMP COMPRISING A GLASS BULB CONTAINING A LIGHT SOURCEAND HAVING ON SAID BULB A COATING OF AN ORGANIC PLASTIC LACQUER COMPOSEDESSENTIALLY OF THE DRIED PRODUCT OF A MATERIAL SELECTED FROM THE GROUPCONSISTING OF THE ACRYLIC ACID ESTERS, CELLULOSE ESTERS AND MIXTURES OFVINYL RESINS AND CELLULOSE ESTERS, AND ABOUT 15 TO ABOUT 400 CUBICCENTIMETERS OF AN ESTER OF SILICIC ACID PER GALLON OF SAID LACQUER.